The present invention relates to a display control and touch detection device, and a semiconductor integrated circuit for display control and touch detection, and it relates to a technique useful in application to a portable information terminal device, e.g. a tablet or a smart phone.
A portable information terminal device, such as a tablet or a smart phone has a panel module disposed on a surface thereof; the panel module is arranged by putting together or integrally forming a display panel and a touch panel. Such a portable information terminal device is able to determine, from touch coordinates, a touch operation performed on the surface of the touch panel by a finger or the like according to a screen display on the display panel in the event of the touch operation. In a mutual capacitance type touch panel supporting a multipoint touch or the like, many detection capacitances are formed at intersecting points of drive and detection electrodes arranged to cross each other like a matrix; detection signals are formed by integrating electric potential changes arising on the detection electrodes through the detection capacitances while driving the drive electrodes sequentially. With a finger located in the vicinity of the detection capacitance, a synthetic capacitance value resulting from the combination with the detection capacitance becomes smaller owing to the stray capacitance of the finger. The touch panel is arranged so that discrimination can be made between a touch and a non-touch based on the difference in detection signal depending on the capacitance value change. The touch panel of this type is disclosed in e.g. U.S. Patent Application No. 2007/0257890A1.
A liquid crystal panel has scan electrodes and signal electrodes, which are arranged to cross each other, and thin film transistors disposed at their intersecting points; the thin film transistors are each referred to as “TFT”. The thin film transistors are arranged in such a way that the gate of each transistor is connected to the corresponding scan electrode, the source is connected to the corresponding signal electrode, and a liquid crystal element and a storage capacitor which make a sub-pixel are connected between the drain and a common electrode, whereby respective pixels are formed. In display control, the scan electrodes are activated sequentially. Thus, the thin film transistors are turned ON for each scan electrode and an electric current is caused to flow between the source and drain, during which signal voltages put on the source electrode lines are applied to the respective liquid crystal elements, consequently bringing them into a transmission state. Such a TFT liquid crystal panel is described in e.g. Japanese Unexamined Patent Publication No. JP-A-2006-301655.
In another patent document, JP-A-2012-234475, there is the description concerning the problem that with drive pulse voltages raised for activating scan electrodes of a touch panel, the noise exerts an adverse effect on a liquid crystal panel through the capacitive coupling, etc. between the display panel and the touch panel which are superposed on each other or integrally formed. In JP-A-2012-234475, a measure is taken by making possible to select the waveform of drive pulses for driving the scan electrodes.
In addition, the influence of noise attributed to the capacitive coupling, etc. between the display panel and the touch panel which are superposed on each other or integrally formed reaches even the display panel to the touch panel. The fact has been considered in JP-A-2014-146093. According to this, the noise coming from the action for driving/display of a display panel, and the noise coming from the action for driving/detection of a touch sensor can be prevented from influencing each other by driving the touch panel and performing the touch detection during a non-display term of the display panel rather than a display term in a cycle of a frame synchronizing signal. The difference in brightness arises in a display frame at each boundary of display and non-display terms especially in a case where the relation of the display and non-display terms is fixed in a cycle of the frame synchronizing signal; the larger the number of times the display and non-display terms are repeated is, the more remarkable the degradation of display quality owing to the undesired brightness difference is.
Therefore, a display controller arranged so that the start timings of display and non-display terms in the cycle of the frame synchronizing signal of a display frame can be changed at intervals of one or a plurality of cycles of the frame synchronizing signal is adopted in JP-A-2014-146093, which proposes a control device arranged to perform a display action in a display term and to conduct a touch detection action in a non-display term.